Atomizer



Aug. 16, 1955 1 W. HELLER ATOMIZER INVENTOR ewzs WHe//er BY ATTORNEY United States Patent OE ice 2,715,546 Patented Aug. 16, 1955 ATOMIZER Lewis W. Heller, Yardley, Pa., assigner to The Babcock & Wilcox Company, Rockleigh, N. J., a corporation of New Jersey Application September 10, 1949, Serial No. 115,013

16 Claims. (Cl. 299-120) This invention relates to Variable capacity, pressure atomizing liquid fuel burners in which the liquid fuel is delivered to a circular whirl chamber under pressure, through substantially tangentially arranged slots, for discharge from an axial orifice in a hollow-cone spray. The invention is particularly applicable to such burners of the return flow type in which a variable quantity of the fuel is withdrawn from the whirl chamber and returned to its source or to some point in the fuel supply system.

Mechanical atomizing burners of this general type are well known and have been widely used where it is desired to handle a variable load by varying the capacity or fuel delivery rates to the burners rather than by varying the number of burners in operation. Return flow mechanical atomizing burners of this type have been used with several systems of operation. ln one system, the supply pressure is maintained substantially constant and the return ow pressure is varied to regulate the amount of fuel bypassed. In another system, the supply pressure is varied and a substantially constant dierential is maintained between the supply and return ow pressures. Still another system, which is described more particularly in the c0- pending application of Thomas B. Stillman, filed Septomber 8, 1949, for Liquid Fuel Circulating System for Mechanically Atomizing Liquid Fuel Burner and Method of Controlling the Output of said Burner, now Patent No. 2,702,590, issued February 22, 1955, concurrently Varies both the supply and return ow pressure whereby a varying differential between supply and return ow pressures is effected in attainment of a regulation of the fuel delivery rate through a wide capacity range.

In return flow burners, the amount of by-passed fuel can be controlled by a control valve located in the return ow passage and controlling the return ilow pressure. If it is desired to operate as a straight mechanical atomizer, its control valve can be completely closed so that all the fuel is discharged through the orice.

The most important operating features of a pressure atomizing liquid fuel burner, in addition to its range of capacity, are its variation in spray angle and the quality of atomization. A constant spray angle is desirable to insure complete and ecient combustion at all capacities by precluding the danger of furnace wall carbonization, furnace hot spots, or contact with the burner parts. It has been found that the spray angle tends to increase with a decrease in the amount of liquid fuel discharged from the atomizer orice. A line quality of atomization under all operating conditions is essential to insure rapid, uniform and complete vaporization and combustion. The wider range of capacity attainable with return-How atomizers is frequently at the expense of spray angle variation and quality of atomization.

The present invention is directed to an improved arrangement for withdrawing liquid fuel from the whirl chamber whereby fuel leaving the chamber has. a minimum impedance imposed upon its ilow, and has a minimum disturbing eiect upon the fuel whirling in the whirl chamber. To this end, the withdrawal means is so arranged as to provide for fuel flow thereinto, from the whirling mass of fuel, with substantially no change in the flow direction of the Withdrawn fuel or interruption to its whirling motion. More specifically, an annular slot or passage opens into the whirl chamber rearwardly of the oil inlet passages, and the flow direction into such slot or passage is substantially normal to the lateral confining surface of the whirl chamber at the withdrawal zone. The cross sectional area of the slot or passage increases rapidly in a direction outwardly from the whirl chamber by virtue of the fact that the passage is essentially frustoconical, diverging rearwardly relative to the whirl chamber axis, and the walls of the passage diverge from each other in a rearward direction. As a result, the velocity head of the withdrawn fuel is rapidly transformed into an increase in the static pressure head of the fuel. The Withdrawn fuel consequently enters axially directed openings, connecting the annular passage to an axial return ow conduit at a very substantially reduced velocity. As a result of the foregoing, the withdrawal of the fuel has a minimum disturbing effect of the fuel whirling in the whirl chamber.

Preferably, the rear portion of the whirl chamber is spherically concave but, for practical manufacturing reasons, is generally made truste-conical and rearwardly converging. However, if desired, the whirl chamber rear portion may be made uniform in cross sectional area or even rearwardly diverging. The portion of the whirl chamber at the intersection of the tangential inlet passages is cylindrical and merges smoothly with a frustoconical section terminating at the axially or centrally arranged discharge orifice.

It is an object of the present invention to provide, in a pressure atomizing liquid fuel burner of the return ow type, an improved return-flow or by-pass arrangement assuring greatly reduced impedance to the iii id movement in the whirl chamber, particularly adjacent the returnow portion.

Another object is to provide a novel whirl chamber configuration effecting improved quality of atomization and improved spray angle variation.

A further object is to provide a novel whirl chamber configuration which contributes to effective utilization of the liquid fuel entry velocity in maintaining maximum angular velocity conditions.

rThese and other objects, advantages and novel features of the invention, will be apparent from the following description and the accompanying drawings. In the drawings:

Fig. l is an elevation view, partly in section and broken along its length, of a liquid fuel burner according to the present invention;

Fig. 2 is an enlarged axial sectional view through an atomizer assembly according to the invention;

Fig. 3 is an enlarged axial sectional view of the atomizer assembly shown in Fig. l;

Fig. 4 is an elevation View of the furnace face of a primary nozzle or plug member of the atomizer assembly of Figs. l and 3;

Fig. 5 is a longitudinal sectional view on the line 5 5 of Fig. 4;

Fig. 6 is an elevation View of a secondary nozzle of the atomizer assembly of Figs. l and 3;

Fig. 7 is a diametric sectional View on the line 7-'7 of Fig. 6; and

Fig. 8 is a sectional View, on the line 8-8 of Fig. 3, of a sprayer or orice plate of the atomizer assembly.

In the liquid fuel burner illustrated in Fig. l, the atomizing parts are disposed within a tube or distance piece 10 having its furnace, forward, or discharge end normally positioned in or adjacent a fuel burner portN of the furnace wall. lf desired, tube 1i) may be flared andV carry an impeller plate 11. In the particular burner shown by way of example only, the outer end of the distance piece may be threaded into a coupling 12 in which is formed a pair of parallel passages 13 and 14 serving as the liquid fuel supply and return flow passages, respectively. The coupling passages register with corresponding passages 15 and 16 in a body member 17 when coupling 12 is secured to member 17 by a coupling yoke 18 adapted to be held in its closing position by a T-handle set screw 19. The described burner construction is exemplary only, and the invention principles are applicable equally to other burners differing in constructionY from that shown.

The vfuel supply and return ow passages 15,-16 of coupling member 17 are connected, respectively, to conduits or tubes 21 and 22 threadedly connected to the atomizer head or assembly. Tube 21 is concentric with and of largerdiameter than tube 22 so that the tubes form an annular fuel supply passage 20, between tubes 21 and 22, and a central return ow passage 25 within tube 22. The furnace or inner ends of passages 20 and 25 communicate with the fuel supply and return flow portions, Arespectively of the pressure atomizing head or assembly 30.

Y In accordance with the present invention, it has been found that high quality atomization over a wide range, together with adequate control of the width of the spray angle over a corresponding range, can be effected by a Vnovel arrangement of the return ow take-off from the whirl chamber and further improved results can be obtained by providing a novel configuration for at least the rear portion of the whirl chamber. The return flow or take-off means is formed as an annular slot or passage opening into the lateral surface of the whirl chamber rearwardly of theV liquid fuel .inlet means thereto.V

The arrangement is such that the V,direction of flow into the take-off slot or passage is substantially normal to the lateral surface of the rear portion of the whirl chamber, and the cross sectional area of the take-off passage increases rapidly outwardly of the whirl chamber. To accomplish this, the general configuration of the takeoff passage is frusto-conical and rearwardly diverging,

Y the passage walls being defined by a pair of concentricV frusto-conical sections having their conical or lateral surfaces in laterally spaced relation to define the takeoff passage. Therwalls of the passage preferably diverge from each other in a rearward'direction.

Preferably,V the portion of the whirl chamber rearwardly of the tangentially arranged inlet passages is spherically concave to obtainV a minimum Wall area to volume ratio to reduce flow impedance. This preferred arrangement is shown in Fig. 2. For practical manufacturing reasons of simplicity and economy, however, the rear portion of the whirl chamber is made Yfrustoconical, asV shown in Figs. l and 3 through 7, as the slight change in shape of the whirl chamber is more than compensated by the reduction in manufacturing costs and complexities. Under certain circumstances, however, the rear Vportion of the whirl chamber may be uniform in cross-sectional area or even rearwardly diverging.

' Reference will be had first to the arrangement of Fig. 2 and, in the arrangement of Figs. l and?)Y through 7, corresponding parts have been'given the same reference characters primed. The furnace end of tube 22 is threaded into the rear end of a cylindrical primary nozzle or plug member 23 having a sealing contact with the ends of tubes 21 and 22. YPrimary nozzle 23 has an annular slot 24 in its furnace face connected by a circular series of passages 26 to annular fuel inlet passage 20. The furnace face of the primary nozzle also has a smaller diameter annular slot 27, dening a central, substantially frusto-conical protuberance 2S and connected by a circular series of apertures 29 to the central fuel outlet or return ow passage 25. For a purpose to be described, the furnace face 31 of protuberance 28 is spherically concave.

The furnace face of primary nozzle 23, when atomizer 30 is assembled, contacts with the outer face of a secondary nozzle or inner tip member 40. The latter has a central passage 33 therethrough, defined by a spherically concave wall 34 which, with the spherically concave face 31 of protuberance 28, constitutes the'outer or rearward, and substantially hemispherical portion of a mixing or whirl chamber 35. The wall of passage 33 is so related to protuberance 28 as to form therewith an annular slot or passage 36, around the protuberance and connecting the rear portion of whirl chamber 35 to slot 27. It will be noted that the general direction of slot 36 is substantially normal to wall 34, and that the slot is substantially frusto-conical and rearwardly diverg-V ing. Hence, the cross-sectional area of slot 36 increases rapidly rearwardly or outwardly from wall 34. An annular slot 37 is formed in the furnace face of second- :ry nozzle 40 in alignment with slot 24 and'connected therewith by a circular series of short passages. 38.

The furnace face of nozzle 40, beyond slot 37,'contacts with the outer face of a sprayer, or orifice plate, or outer tip 50, which has a portion of its periphery cut away'to provide a seat for an end cap 55 which is screwed on theouter tube 21 to hold the primary nozzle, secondary noz-` zle and sprayer plate in their desired assembled position. Sprayer plate 50 has a central cylindrical opening 42 aligned with passage 33 to form an intermediate portion f Whirl chamber 35. Opening 42 Vis connected. by .a frusto-conical passage 43 to a discharge orifice 44 of smaller diameter than the whirl chamber 35. The outer face of sprayer plate 50 is formed with a plurality of slots 46 each tangential to passage or opening 42 and communicating, at their outer ends, with slot 37 of nozzle member 40. Y

With the foregoing construction, liquid fuel, such as oil, under a substantial pressure, is delivered to inlet passage 20 from which it passes through holes 26, slot 24,

holes 38, and slot 37 into tangential slots 46.in orificeY plate 50. Due to the tangential arrangement of slots 46,. f

the oil follows a spiral path in whirl chamber 35 toward discharge orifice 44. lf vthe Vatomizer is operated as a return-flow atomizer, a variablev portion of the oil, dependent upon the relation between the supply and return pressures, follows a spiral path toward slot 36 from fuel, as there is no change in Vthe flow direction of thev y withdrawn fuel. The substantially normal relation of slot or passage 36 to wall 34 provides for effective utilization of the centrifugal force of the whirling liquid fuel Y in directing the return flow into passage 36. The rearward or outward divergence of the annular passage 36.*Y provides a rapid increase in the cross-sectional area of the passage outwardly ofthe whirl chamber. Consequently, the velocity head of the liquid fuel is correspond` ingly effectively reduced and converted into an increased static pressure head as the fuel flows outwardly through passage 36 into annular slot 27, from which it passesY through passages 29 into return-flow passage 25 ofvtube or conduit 22.

The oil dischargedV through orifice 44 emerges as a spray of hollow, conical configuration and a substantially constant angle over a wide range of atomizer capacity. Due to the spherically concave shape of the outer or rear portion of whirl chamber 35 and the smooth withdrawal of the return-flow fuel, the oil is discharged from orifice 44 as a substantially uniform, whirling spray cone. When the atomizer is operated as a straight mechanical atomizer, with return ow passage closed by a valve there is a substantially solid body or mass of oil in passage 25, holes 29, and slots 27 and 3e. The eect is to provide a substantially non-interrupted, hemispherical surface for the rear or outer portion of the whirl chamber, resulting in a substantially non-turbulent discharge from orifice 44.

In the modified atomizer assembly shown in Figs. l and 3 through 7, the inner end of tube 22 is threaded to engage a cylindrical primary nozzle or plug member 23 which is generally similar to nozzle 23 and has a sealing contact with the furnace ends of tubes 2l and 22. Nozzle 23', as best shown in Figs. 4 and 5, has an annular slot 24 in its furnace face connected by a circular series of passages 26 to annular fuel inlet passage 25. The furnace face of nozzle 23' also has a smaller diameter annular slot 27 defining a central, substantially frusto-conical protuberance 2S which projects beyond the forward face of the remainder of the nozzle 23. Slot 27 is connected by a circular series of apertures 29 to the central fuel outlet or return passage 2). Protuberance 23 is frusto-conical and has a fiat or plain furnace face 31.

The furnace face of nozzle 23', when atomizer 3Q is assembled, contacts with the outer face of a secondary nozzle or inner tip member 4u', shown more particularly in Figs. 6 and 7. The latter has a central passage 33 therethrough, which is cylindrical. Toward the outer face of nozzle passage 33 connects with a frustoconical rearwardly diverging passage S3 and toward the furnace face of nozzle 40', passage 33 communicates with a frustoconical forwardly dii/erging passage 34. The wall of passage 53 is so related to protuberance 28 as to form an annular passage 36 around the protuberance and connecting whirl chamber 35 to slot 27. An annular slot 37 is formed in the furnace face of secondary nozzle dil in alignment with slot 24 and connected therewith by a circular series of short passages 3S.

The furnace face of nozzle dil', beyond slot 37', contacts with the outer face of a sprayer, or orifice plate or outer tip 5S', best shown in Figs. 3 and 8. Orice plate S has a portion of its periphery cut away to provide a seat for an end cap S5 which is identical with cap 55 and is screwed on outer tube 21 to hold primary nozzle, secondary nozzle, and sprayer plate in their desired assembled position. Sprayer plate 50 has a central cylindrical opening 42 forming a continuation of frustoconical forward passage 34 to nozzle 4%. Opening 42 is connected by a frusto-conical forwardly converging passage 43 to a discharge orifice 44 of whirl chamber 45. The outer face of sprayer plate 56 is formed with a plurality of slots 4u', each tangential to passage or opening 42', and communicating at the outer ends with slot 37 of nozzle member 49.

This embodiment of the atomizer assembly operates in the same manner as does that of the sprayer assembly shown in Fig. 2. The return ow liquid fuel is drawn olf in a non-turbulent manner through the annular slot 36 at the rear of whirl chamber 3S', which provides for fuel flow thereinto without change in flow direction, The rear portion of the whirl chamber, in advance of slot 36 is substantially frusto-conical, thus being somewhat simpler as regards the manufacture of the atomizer assembly than is the spherical rear whirl chamber portion of Fig. 2. The rear wall of the whirl chamber is formed by the flat face 3l of protuberance 28 which cooperates with outer nozzle 40 to form the return fiow Vslot 36.

The diverging annular slot 27, formed by wall section 53 and the lateral surface of protuberance 28', has a general ow direction substantially normal to the frustoconical surface 34' of the rear portion of whirl chamber 3S. Also, the cross-sectional area of slot 27 increases rapidly outwardly of chamber 35. These features effect the improved performance in the same manner as` does slot 27 of Fig. 2.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be otherwise embodied without departing from such principles.

I claim:

l. A return-flow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber, a discharge orifice at one end thereof, and a rear wall; fuel Supply passage means communicating tangentially with such inlet zone; means for removing a portion of the fuel whirling in such chamber comprising an annular return flow slot communicating peripherally with the rear wall of the chamber and increasing uniformly in diameter and cross-sectional flow area outwardly of the whirl chamber; and a return ow passage communicating with such return flow means.

2. A return-dow liquid fue] burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber, a discharge orifice at the forward end thereof, and a rear wall; fuel supply passage means communicating tangentially with such inlet zone; means for removing a portion of the fuel whirling in such chamber comprising a return liow passage communicating with an annular slot opening through the rear wall of the chamber and diverging uniformly outwardly from the whirl chamber; and a return flow conduit communicating with such return flow passage.

3. A return-iiow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber and a discharge orice at one end thereof; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising a return flow passage opening through the surface of such chamber throughout the chamber circumference rearwardly of such inlet zone, such passage extending substantially normal to the lateral surface of the whirl chamber and increasing uniformly in diameter and cross-sectional area outwardly from such lateral surface.

4. A return-now liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the Whirl chamber and a discharge orifice at one end thereof, the whirl chamber progressively decreasing in cross sectional area from such inlet zone to the opposite `end of the whirl chamber; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising an annular return ow passage opening to such chamber through the surface of such opposite end and throughout the chamber circumference and increasing uniformly in diameter and cross-sectional area outwardly from such surface.

5. A return-flow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber and a discharge orifice at one end thereof, the whirl chamber decreasing in cross sectional area at a progressively increasing rate from such inlet zone to the opposite end of the whirl chamber; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising a return flow passage opening to such chamber through the surface of such opposite end and throughout the chamber circumference and increasing uniformly in diameter and cross-sectional area outwardly from such surface.

6. A return-now liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber and a discharge orifice at one end thereof, the whirl chamber decreasing in cross sectional area substantially uniformly from such inlet zone to the opposite end of the whirl chamber; a fuel supply passage` communicating `tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising a return flow passage opening to suchrchamber through the surface of such opposite end and throughout the chamber circum-` ference and increasing uniformly in diameter and cross# sectional area outwardly from such surface.

7. A return-flow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate Vthe length of the whirl chamber, an axial discharge orifice at one end thereof, and a rear wall; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a portion of the fuel whirling in such chamber comprising an annular return flow passage opening peripherally through such rear wall of the chamber rearwardly of the inlet zone; the radially inner and outer walls of said passage being at an acute angle to the axis of the whirl chamber.

8. A return-flow liquid fue] burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet zone intermediate the length of the whirl chamber, an axial discharge orifice at one end thereof, Vand a rear wall; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising an annular return flow pas- Y sage communicating with an annular slot opening through the rear wall of such chamber rearwardly of the inlet zone; the radially inner and outer walls of such passage being substantially normal to the lwall of the chamber and at an acute angle to the axis of the chamber.

9. A return-flow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including Va fuel inlet zone intermediate the length of the whirl chamber, an axial discharge orifice at one endrthereof, and a rear wall; a fuel supply passage communicating tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising a return flow passage communicating with an annular slot opening through the rear wall of such chamber rearwardly of the inlet zone Y and throughout the chamber circumference; the diameter and cross sectional ow area of such slotV increasing rapidly and uniformly outwardly from the whirl chamber. l0. A return-flow liquid fuel burner comprising, in combination, means forming'a whirl chamber of circular cross section including a fuel inlet zone intermediate the length 'of the Whirl chamber and an axial discharge orifice Vat the forward Vend thereof, the surface of the whirl chamber rearwardly of the inlet zone being substantially hemispherical; a fuel supply passage communicaring tangentially with such inlet zone; and means for removing a peripheral portion of the liquid fuel whirling in such chamber comprising an annular slot in such hemispherical surface rearwardly of such inlet zone anda return flowrpassage communicating with such slot.

ll. A return-flow liquid fuel burner comprising, in combination, means forming a whirl chamber of circular cross section including a fuel inlet Zone intermediate the length of the whirl chamber and an axial discharge orifice at the forward end thereof, the surface of the whirl chamber rearwardly ofthe inlet zone being substantially frusto-conical and decreasing in radius rearwardly of such inlet zone to av reduced diameter throat; a fuel supply,

l2. A spill burner comprising a hollow member defining aswirl chamber which is symmetrical about an axis, and having inlet orifices tangentially admitting to said chamber, an axially centered circulardischarge orifice formed at one end of said swirl chamber, of a diameter small in comparison to the maximum diameter of the chamber itself, and an axially centered circular spill open- K ing formed in the opposite end of said swirl chamber, aV stem which is symmetrical about the swirl chambers axis, means located wholly outside the swirl chamber to support said stem in position wherein it projects into the spill opening, said stem being of a shape and maximum diameter, in relation to said spill opening and to the discharge orifice, to define, in such position, a wholly uninterrupted annular spill orifice which is of capacity at least equal to the sum of the capacities of said tangential inlet orifices.

13. A spill burner comprising a hollow member defining a swirl chamber and a separate diffusing chamber each of which is symmetrical about and aligned along a common axis, said holiow member having inlet orifices tangentially admitting to said swirl chamber, an axially centered circular spill opening affording communication between the swirl chamber and the diffusing chamber, and an axially centered circular discharge orifice leading from the end of the swirl chamber which is distant from said spill opening, and of a diameter Which is small with respect to both the maximum diameter of the swirl chamber and the minimum diameter of the spill opening, a stem which is symmetrical about the chambers axis, supported entirely from that wall of the diffusing Vchamber which is opposite the spill opening, and projecting thence into the spill opening, said stem being of a shape and maximum diameter, in relation to said spill opening and to the discharge orifice, to define a whollyunint'errupted annular spill orifice which is of a capacity at least equal to the sum of the capacities of said tangential inlet orifices.

I4. A spill burner comprising hollow means defining a swirl chamber of round cross-section having tangentially arranged inlet openings in its peripheral wall, a discharge orifice axially located at its forward end, and a rear wall opposite said discharge orifice, said rear wall Vbeing axially apertured, inwardly fromthe chamber-s peripheral wall, to leave a surrounding annular portion as part of d the rear wall, and an element supported rearwardly of opposite said discharge orifice, said rear wall having al Y single, circular, axially located discharge aperture, said passage communicating tangentialiy with such inlet zone; Y

and means for removing a peripheral portion of the liquid.

surface, and arreturn flow passage communicating with such slot.

hollow member being enlarged radially, rearwardly of said discharge aperture, to define a diffusing chamber located substantially wholly radially outwardly of said discharge aperture, Van element ported for further discharge but otherwise closing and defining the rearend of said diffusing chamber, said element havingan axially dirsposed forward extension projecting within the discharge aperture of the swirl chamber, spaced within the margin of such discharge aperture to define therewith an annular spill orifice which isA wholly uninterrupted circumferentially, from the swirl chamber vto the rear end of the diffusing chamber, and a capacity at least as great as the sum of the capacities of the tangential inlet openings.

16. A spill burner comprising hollow means having a cylindrical peripheral wall forming a swirl chamber having tangentially arranged inlet orices, and a circular discharge orifice axially located in the forward end thereof and of a diameter small in comparison to said cylindrical wall, said swirl chamber having also a rear wall closing the opposite end of said swirl chamber 1out having axially located therein a circular spill opening larger in diameter than said discharge orifice but smaller than the peripheral wall, a solid member of circular transverse section projecting into said spill opening in spaced coaxial relation therewith, from a location beyond the rear wall of said swirl chamber into the vicinity of such rear wall, said solid member defining in conjunction with said spill opening, a continuous annular spill orice of capacity at least as great as the sum of the capacities of said inlet orices, and located wholly outwardly of the axial projection of said discharge orice.

UNTED STATES PATENTS References Cited in the file 0f this patent 1,644,372 Gray Oct. 4, 1927 1,326,488 Fisher Dec. 30, 1919 2,037,645 Vroom Apr. 14, 1936 2,079,430 Bargeboer May 4, 1937 2,308,909 Blanchard Ian. 19, 1943 2,373,707 Peabody Apr. 17, 1945 2,374,041 Saba Apr. 17, 1945 

